1. Field of Invention
Calorimeters have been known for a long time and are used to screen reactions, particularly during the process development in the chemical industry. In doing so, chemical reactions are examined regarding their thermodynamics and kinetics. Essential parameters are the reaction enthalpy, the thermal capacity, and the specific reaction rates, for example.
Calorimeters measure heat flows of chemical reactions and physical conversions. Isothermal, adiabatic, isoperibolic and temperature-programmed variants are being offered. When examining chemical reactions to determine thermokinetic data, isothermal measuring conditions are often preferred in practical operation. Isothermal reaction conditions are particularly advantageous when calometry and online analytics are combined, as the corresponding signals can change as a function of the temperature. Ensuring isothermal reaction conditions with the conventional technology requires a considerable expenditure on equipment.
Calorimeters that permit isothermal experiment conditions may be divided into the following types: heat flow, heat balance and power compensation. The basis for these three calorimetric measuring methods is the heat flow balance of the reaction vessel. The required reaction heat as a function of time can be calculated via the heat flow balance, provided that all other components in the balance, especially the stirring energy, the heat flows through the reactor wall, and other heat loss flows, are known. All three types have in common the problem of the fluctuating heat transmission on the interior reactor wall during the course of a chemical reaction. Corresponding processes must be taken into account in the heat flow balance, either mathematically or experimentally. Experimental methods are always preferred over mathematical ones since the exact interrelationships are not known for a general system.
2. Description of Related Art
A calorimeter with an intermediate thermostat into which the reactor is built in, as well as with an external thermostat, has become known in the prior art from German patent application DE-A-3049105. It essentially consists of a reactor with an agitator wherein isothermal conditions are maintained during the course of a reaction by means of a regulated heater. An apparatus is used to measure the electrical output that is required to maintain the isothermal conditions. This calorimeter operates according to the above-mentioned principle of the so-called power compensation. The temperature is highest inside the reactor and a median temperature exists in the intermediate thermostat. The lowest temperature is inside the main thermostat. In accordance with the constant temperature difference between the reactor and the intermediate thermostat, a heat flux flows from the reactor into the intermediate thermostat, and a further heat flux flows from the intermediate thermostat into the main thermostat. When a reaction starts in the reactor, a regulator that is connected to a heater ensures that the temperature difference between the reactor and intermediate thermostat remains constant during the course of the reaction, despite the beginning reaction heat. An intermediate thermostat wall is formed by a tube coil system, through which the thermostat liquid of the main thermostat flows in a turbulent flow. The thermostat liquid usually is a liquid heat carrier that flows around the reaction vessel on the outside and can be regulated to a desired temperature. Permitting the thermostat liquid to flow around the reactor requires a double jacket. A double jacket of this type poses the problem, in particular, that local inhomogenities may occur within the same. Furthermore, the production and thermoregulation of a double-walled reaction vessel are expensive. Performing applications under pressure is difficult or impossible. A further shortcoming lies in the fact that the reactor volume is comparatively large, and correspondingly large quantities of the test substance must be produced. The large dimensions and complexity of the thermoregulating system have as a result that parallel operations would be expensive.
A further calorimeter is revealed in U.S. Pat. No. 4,456,389. This calorimeter is also provided with a double jacket containing a thermostat liquid that is circulated by means of a pump. This calorimeter permits isothermal experiment conditions, however, it has a comparatively large volume. The heat flow principle that is used here results in comparatively sluggish equipment with respect to quickly changing heat flows. The above-mentioned problem of the fluctuating heat transmission of the interior reactor wall during the reaction cannot be fully experimentally addressed with this calorimeter. Parallel operations would be expensive for reasons analogous to the above example.
The invention has as its object to create a calorimeter of the above type that avoids the above-mentioned problems. The inventive calorimeter shall be implementable with a significantly more simple design and nevertheless provide exact measurements. Furthermore, it shall be possible to equip it, in a simple manner, with further analysis methods such as, for example, an IR sensor.